A critical aspect in the safe use of sources of ionising radiation for the protection of personnel is the constant monitoring of radiation levels in the working environment.

The national statutory requirement for the monitoring of ionising radiation in the workplace and the regular testing of appropriate monitoring equipment has applied equally to the specialised areas of alpha-, beta-, photon- and neutron radiations. This statutory obligation was strengthened with the establishment of the Health and Safety Commission and the Health and Safety Executive and the publication of the 1999 Ionising Radiations Regulations and Code of Practice 'The protection of persons against ionising radiation arising from any work activity'.

Although scientists have been measuring cosmic radiation since early last century, it is only recently that the implications of the increased radiation levels at aircraft altitudes have been considered important. This stems from changes in radiation protection legislation, which now regards workers whose exposure to natural radiation is increased as a direct consequence of their work in much the same way as 'traditional' radiation workers, such as those employed by the nuclear industry. This same legislation also for the first time sets limits on levels of radiation as a result of exposure in the home, primarily from Radon gas.

Current regulations and Codes of Practice require that radiation-monitoring instruments are regularly tested and calibrated to a known accuracy in relation to national standards. In general, this equipment will be suitable for either the assessment of the radiation dose received by the individual in the course of their work (individual monitoring) or the routine assessment of radiation levels in working environments (area monitoring).